1. Field of the Invention
The invention relates to a compressor wheel for a turbocharger, in particular in combination with a diesel engine, to an exhaust gas turbocharger comprising a compressor wheel, and to a process for producing the compressor wheel.
2. Description of the Related Art
Exhaust gas turbochargers are systems intended to increase the power of piston engines. In an exhaust gas turbocharger, the energy of the exhaust gases is used to increase the power. The increase in power and reduction in emissions are the result of an increase in the throughput of mixture per working stroke.
A turbocharger substantially comprises an exhaust gas turbine with a shaft and a compressor, wherein the compressor wheel arranged in the intake tract of the engine is connected to the shaft and the blade wheels located in the casing of the exhaust gas turbine and the compressor rotate.
Exhaust gas turbochargers that allow multi-stage, i.e. at least two-stage, supercharging, such that even more power can be generated from the exhaust gas, are known. Multi-stage exhaust gas turbochargers of this type have a special design which comprises, inter alia, a regulating member for highly dynamic, cyclic stresses.
Extremely high demands are made on the material of the compressor wheel in the exhaust gas turbocharger. The material from which the compressor wheel is formed has to be heat-resistant and also has to be able to withstand high temperatures, i.e. still has to provide sufficient strength and additionally a good vibration resistance even at high temperatures of at least up to about 220° C. or even 280° C. Furthermore, the material has to be resistant to intercrystalline corrosion and stress crack formation in the acid medium, and it should also have a high material resistance in the case of a low number of stress cycles. In addition, the ductility of the material should be sufficiently high such that, in the event of overload, the parts can experience plastic deformation and do not break, which might result in the sudden release of energy with resulting damage.
An exhaust gas turbocharger with a two-flow exhaust gas inlet duct is known from DE 10 2007 018 617 A1.
Therefore, it was an object of the present invention to provide a compressor wheel for a turbocharger, and a turbocharger, which has an improved heat resistance and thermal stability and is distinguished by a good resistance to corrosion and stress crack formation in acid media. In addition, it was an object to provide a compressor wheel which has optimum ductility and an improved vibration resistance performance. It should thus be possible to produce a wear-resistant, highly vibration-resistant and permanently stable compressor wheel which tends toward neither stress crack formation nor intercrystalline corrosion, even at low pH values. Furthermore, it was an object to provide a process for producing the compressor wheel according to the invention, a material distinguished by the advantageous properties mentioned above being produced by means of said process.